They were probably either trying to catch bait or were actually fishing, probably for catfish. I've been under there many times to catch yellowtail for stripe fishing, mainly in the Spring. As someone mentioned, when they are generating, the water boils out past the base of the dam, so there is actually a reverse current that pushes you back towards the dam wall. This could be a little scary if you weren't expecting it. I've seen some boats stay under there all day long. The only incident we ever had was a pipe about 12" diameter and about 8 feet above the waterline suddenly started discharging water into our boat. It only lasted long enough for us to move, and that's the only time I ever saw anything come out of that pipe. CD.